Re: [Discuss-gnuradio] switching between signal and reference source

[Johnathan Corgan]

On Thu, Apr 15, 2010 at 16:52, Marcus D. Leech <address@hidden> wrote:

> Can I use the GPIO stuff to give me better confidence of adequate
> synchronization between the
>  actual data, and the state of the input?

If you are willing to give up an LSB, you can turn on GPIO streaming
with enable_gpio_streaming().  Then io_rx[15] will show up in the lsb
of I, and io_rx[14] will show up in the lsb of Q.  You need to use the
usrp2.source_16sc source to get the raw samples, then gr_and_const to
separate the digital bit from the rest of the sample.

The io bits get stuffed as the samples come out of the DDC, so there
is a fixed offset (you'll need to measure it) based on the group delay
through the whole analog front-end and FPGA DDC.  The delay is
decimation dependent, but deterministic.

Johnathan